Is the SSD upgradable - Lenovo IdeaPad Yoga 2 Pro

Computer is probably too old to recognize an SSD. You may be able to find a firmware upgrade. Did you boot into the BIOS and try and find the SSD?

https://www.google.com/search?q=Compaq+presario+c500+dos+not+detect+ssd+hard+drive

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Of course. All PC's have DRAM.
If you want to increase DRAM you can purchase from:
Crucial com DRAM solid state drive SSD memory upgrades for Dell Mac Apple...
they also have a tools to check your system ram size.
Crucial com DRAM solid state drive SSD memory upgrades for Dell Mac Apple...

you cannot change or upgrade your HD to SSD. SSD is a technology in which storage medium is not a disk but a Memory chip just like USb flash drive.
However you can exchange your driver with SSD

amazon allows these questions on the page an will send emails to several to answer this, many go directly to those that purchased that model .

This is a little bit long shot, but check also if there is an updated firmware for the SSD (you will need access to another machine in order to upgrade it). I will look up if I find either a bios for the Dell that is working or another solution

INTEL
KINGSTONE
Samsung are the best brands depends on your budget and arability in your area.

Usually, it is not possible to upgrade the cpu on a laptop. In rare cases where it is possible the upgrade usually costs nearly as much as a new laptop.
However, you can significantly upgrade the laptop's performance by adding more memory and by replacing the old slow hard drive.
Your Sony VGN-Z250 is usually supplied with 3GB of RAM memory. You can replace the existing memory modules with a new kit consisting of 2 x 2GB modules (total 4GB). The type of memory you need is "SO-DIMM" (meaning laptop size) DDR3 - 1066MHz (you may use 1333MHz memory but it will only run at 1066MHz speed). I would suggest either G-Skill or Crucial brand memory. And you can replace the hard drive with an SSD. You'll be amazed at the boost this provides, seriously. I would suggest either Samsung 840 EVO or Sandisk Ultra for an SSD. Both offer super-fast performance compared to your old spinning hard drive, and both have very low power consumption so they run cool and give your laptop a few extra minutes of battery power. You can clone/copy your existing Windows setup onto the SSD using free Macrium Reflect software or free software from the SSD maker's website. Or, you can do a fresh install of Windows.

SSD drives are only limited by whats available right now, and price. However your says its soldered according to these specs. but you should still verify.

http://www.cnet.com/laptops/sony-vaio-z-series/4507-3121_7-34863572.html

It should work as long as the SSD is physically the same size so it will fit in the mac. Before buying the SSD I would check with a local computer repair shop as to whether the mac os can handle that certain SSD. I think it should work fine.

This picture should help you identify the location of the SSD in the drive.dell website doesnt say anything about the SSD upgrade.You can check with them for the exact details.

Numbers reference image above: SSD WWAN Card Memory WLAN Card